Pre-operative preparation of the skin with a topical antimicrobial agent is necessary to reduce the likelihood that the patient will contract a hospital-acquired infection during a surgery or surgical procedure. Typically, the healthcare practitioners, for example, prep nurses, apply a topical antimicrobial agent to a surgical or needle entry site before the procedure. Similarly, it is essential that medical devices that breach the skin be disinfected prior to penetrating the skin at an entry site or accessing an intravenous system. Healthcare practitioners typically disinfect these medical devices by applying an antimicrobial solution, e.g., alcohol, prior to use. Such treatment reduces the infection rate at the site or within the blood stream by hindering the growth of microorganisms or disinfecting a wound, surgical incision, or needle puncture site.
The human skin is normally covered with microorganisms such as bacteria, fungi, and viruses. The microorganisms are either transient, found on the skin's surface or are resident in deeper areas of the skin, such as the hair follicles.
The microorganisms are prevented from entering the body by the physical barrier of skin and the acid mantle, a protective layer formed by the mixture of sweat and sebum. The acid mantle maintains a moderately acidic covering for the normal human skin. The pH means and ranges for the normal skin of both adults and neonates are 5.7±0.16 (range: 4.5-6.7) and 7.08±0.17 (range: 6.6-7.5), respectively.
The function of the acid mantle is not completely understood even though the acidic environment of the skin's surface has been recognized for a century. However, the acid mantle is believed to assist the body in processing the lipids required for the skin to function as a barrier. Acidic environments also generally hinder bacterial growth, and hence, help resist bacterial infection.
Potential pathogens usually cannot enter the body if the skin and acid mantle remain intact. However, the integrity of the skin barrier is breached during surgical procedures, potentially exposing the surgical site or wound to microorganisms, increasing a patient's risk of infection. Thus, standard surgical procedures require that the skin at the surgical site be disinfected prior to surgery to reduce the patient's risk of infection. Therefore, there is a need in the art for a topical agent that will both kill the transient and resident microorganisms quickly and provide sustained antimicrobial activity throughout the entire surgery or surgical procedure.
Healthcare practitioners have long used ethanol or isopropanol, either alone or as a solvent along with other antimicrobial agents, to disinfect the skin at the surgical incision or needle puncture site and medical devices that penetrate the skin since these alcohols quickly reduce the population of bacteria, fungi, and some viruses at the site. Alcohol also provides rapid and sustained antimicrobial activity when it is combined with antimicrobial agents. However, alcohol based surgical prep solutions are flammable and certain surgical procedures cannot begin until the alcohol is completely evaporated. Hospital fires have been caused by unevaporated flammable solvents within surgical prep solutions. For the patient's safety, it is critical that healthcare practitioners be able to determine whether the flammable solvents within surgical prep solutions are completely evaporated prior to initiating energized surgical procedures, for example, electrocautery.
Solvent evaporation in particular presents a major challenge for healthcare practitioners for several reasons. First, it is difficult to visually determine when a colorless solvent (e.g., alcohol) has sufficiently evaporated to begin surgery or the surgical procedure. Second, the healthcare practitioners will often physically touch the skin surface or the medical device with a glove to determine the level of dryness. However, if the skin or medical device is not dry when touched, such a touch may breach the applied prep solution and provide a pathway for microorganisms to enter the body through the skin or via the medical device. Thus, it is necessary and desirable for the healthcare practitioners to have an easy way to determine if a solvent within a surgical prep solution has completely evaporated from the surgical site or the medical device without touching the skin, the medical device, or the applied surgical prep solution.
An effective film forming polymer may also be added to the surgical prep solution to provide better adherence of the solution to the skin or the medical device. Film forming polymers are either water soluble or insoluble and most of the water insoluble films adhere poorly to the skin. Poor adherence is especially problematic in orthopedic surgery or surgical procedures in which patients are draped after the surgical prep solution has dried. If the surgical prep solution adheres poorly to the skin or is water soluble, the drape will typically fall off during the procedure, contaminating the sterile surgical environment and increasing the chance of a hospital-acquired infection.
U.S. Pat. No. 5,763,412 teaches a film-forming composition containing chlorhexidine gluconate. U.S. Pat. No. 5,547,662 (hereinafter “the '662 patent”) is directed to a film-forming composition for preparation of a skin surface as a surgical site containing an antimicrobial agent and Dowicide A and D&C Red 17, which changes color from purple (wet) to red (dry), but does not teach color changes triggered by pH indicators. The disadvantages of the '662 patent include inter alia the particular combination is not applicable to antimicrobial with inherent color, such as iodine or iodophors and the color change is not reversible. In addition, U.S. Pat. No. 4,584,192 teaches chlorhexidine or its derivative, but does not disclose which chlorhexidine compound is suitable and has no visualization feature.